As a carboxyl group-containing polymer, there have been known a copolymer of an α,β-unsaturated carboxylic acid such as acrylic acid and a polyallyl ether (U.S. Pat. No. 2,923,692); a copolymer of an α,β-unsaturated carboxylic acid and hexaallyl trimethylene trisulfone (U.S. Pat. No. 2,958,679); a copolymer of an α,β-unsaturated carboxylic acid and triallyl phosphate (U.S. Pat. No. 3,426,004); a copolymer of an α,β-unsaturated carboxylic acid and glycidyl methacrylate (Japanese Patent Laid-Open No. Sho 58-84819); and the like. The particles of these carboxyl group-containing polymers have been used for uses such as a thickener for cosmetics and a suspension stabilizer for emulsions or suspensions, after the particles are dispersed and swelled in water, and neutralized with an alkali, to give a neutralized viscous liquid.
However, there are some defects in the neutralized viscous liquids prepared by neutralizing the above-mentioned particles of the carboxyl group-containing polymers with an alkali that gloss or the like is insufficient because the gel appearance (surface smoothness) and transparency of the liquids are insufficient. Therefore, if the gel appearance of a neutralized viscous liquid is excellent, there are some defects that it takes a long period of time for agitation, and in some cases, at least 10 hours for mixing with agitation, which differs depending upon the agitation apparatus or the agitation conditions used for the neutralization when the particles are neutralized with an alkali, so that its productivity is not good.